1 /* Common capabilities, needed by capability.o. 2 * 3 * This program is free software; you can redistribute it and/or modify 4 * it under the terms of the GNU General Public License as published by 5 * the Free Software Foundation; either version 2 of the License, or 6 * (at your option) any later version. 7 * 8 */ 9 10 #include <linux/capability.h> 11 #include <linux/audit.h> 12 #include <linux/module.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/security.h> 16 #include <linux/file.h> 17 #include <linux/mm.h> 18 #include <linux/mman.h> 19 #include <linux/pagemap.h> 20 #include <linux/swap.h> 21 #include <linux/skbuff.h> 22 #include <linux/netlink.h> 23 #include <linux/ptrace.h> 24 #include <linux/xattr.h> 25 #include <linux/hugetlb.h> 26 #include <linux/mount.h> 27 #include <linux/sched.h> 28 #include <linux/prctl.h> 29 #include <linux/securebits.h> 30 #include <linux/user_namespace.h> 31 #include <linux/binfmts.h> 32 #include <linux/personality.h> 33 34 /* 35 * If a non-root user executes a setuid-root binary in 36 * !secure(SECURE_NOROOT) mode, then we raise capabilities. 37 * However if fE is also set, then the intent is for only 38 * the file capabilities to be applied, and the setuid-root 39 * bit is left on either to change the uid (plausible) or 40 * to get full privilege on a kernel without file capabilities 41 * support. So in that case we do not raise capabilities. 42 * 43 * Warn if that happens, once per boot. 44 */ 45 static void warn_setuid_and_fcaps_mixed(const char *fname) 46 { 47 static int warned; 48 if (!warned) { 49 printk(KERN_INFO "warning: `%s' has both setuid-root and" 50 " effective capabilities. Therefore not raising all" 51 " capabilities.\n", fname); 52 warned = 1; 53 } 54 } 55 56 int cap_netlink_send(struct sock *sk, struct sk_buff *skb) 57 { 58 return 0; 59 } 60 61 /** 62 * cap_capable - Determine whether a task has a particular effective capability 63 * @cred: The credentials to use 64 * @ns: The user namespace in which we need the capability 65 * @cap: The capability to check for 66 * @audit: Whether to write an audit message or not 67 * 68 * Determine whether the nominated task has the specified capability amongst 69 * its effective set, returning 0 if it does, -ve if it does not. 70 * 71 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() 72 * and has_capability() functions. That is, it has the reverse semantics: 73 * cap_has_capability() returns 0 when a task has a capability, but the 74 * kernel's capable() and has_capability() returns 1 for this case. 75 */ 76 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, 77 int cap, int audit) 78 { 79 for (;;) { 80 /* The creator of the user namespace has all caps. */ 81 if (targ_ns != &init_user_ns && targ_ns->creator == cred->user) 82 return 0; 83 84 /* Do we have the necessary capabilities? */ 85 if (targ_ns == cred->user->user_ns) 86 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; 87 88 /* Have we tried all of the parent namespaces? */ 89 if (targ_ns == &init_user_ns) 90 return -EPERM; 91 92 /* 93 *If you have a capability in a parent user ns, then you have 94 * it over all children user namespaces as well. 95 */ 96 targ_ns = targ_ns->creator->user_ns; 97 } 98 99 /* We never get here */ 100 } 101 102 /** 103 * cap_settime - Determine whether the current process may set the system clock 104 * @ts: The time to set 105 * @tz: The timezone to set 106 * 107 * Determine whether the current process may set the system clock and timezone 108 * information, returning 0 if permission granted, -ve if denied. 109 */ 110 int cap_settime(const struct timespec *ts, const struct timezone *tz) 111 { 112 if (!capable(CAP_SYS_TIME)) 113 return -EPERM; 114 return 0; 115 } 116 117 /** 118 * cap_ptrace_access_check - Determine whether the current process may access 119 * another 120 * @child: The process to be accessed 121 * @mode: The mode of attachment. 122 * 123 * If we are in the same or an ancestor user_ns and have all the target 124 * task's capabilities, then ptrace access is allowed. 125 * If we have the ptrace capability to the target user_ns, then ptrace 126 * access is allowed. 127 * Else denied. 128 * 129 * Determine whether a process may access another, returning 0 if permission 130 * granted, -ve if denied. 131 */ 132 int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) 133 { 134 int ret = 0; 135 const struct cred *cred, *child_cred; 136 137 rcu_read_lock(); 138 cred = current_cred(); 139 child_cred = __task_cred(child); 140 if (cred->user->user_ns == child_cred->user->user_ns && 141 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 142 goto out; 143 if (ns_capable(child_cred->user->user_ns, CAP_SYS_PTRACE)) 144 goto out; 145 ret = -EPERM; 146 out: 147 rcu_read_unlock(); 148 return ret; 149 } 150 151 /** 152 * cap_ptrace_traceme - Determine whether another process may trace the current 153 * @parent: The task proposed to be the tracer 154 * 155 * If parent is in the same or an ancestor user_ns and has all current's 156 * capabilities, then ptrace access is allowed. 157 * If parent has the ptrace capability to current's user_ns, then ptrace 158 * access is allowed. 159 * Else denied. 160 * 161 * Determine whether the nominated task is permitted to trace the current 162 * process, returning 0 if permission is granted, -ve if denied. 163 */ 164 int cap_ptrace_traceme(struct task_struct *parent) 165 { 166 int ret = 0; 167 const struct cred *cred, *child_cred; 168 169 rcu_read_lock(); 170 cred = __task_cred(parent); 171 child_cred = current_cred(); 172 if (cred->user->user_ns == child_cred->user->user_ns && 173 cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) 174 goto out; 175 if (has_ns_capability(parent, child_cred->user->user_ns, CAP_SYS_PTRACE)) 176 goto out; 177 ret = -EPERM; 178 out: 179 rcu_read_unlock(); 180 return ret; 181 } 182 183 /** 184 * cap_capget - Retrieve a task's capability sets 185 * @target: The task from which to retrieve the capability sets 186 * @effective: The place to record the effective set 187 * @inheritable: The place to record the inheritable set 188 * @permitted: The place to record the permitted set 189 * 190 * This function retrieves the capabilities of the nominated task and returns 191 * them to the caller. 192 */ 193 int cap_capget(struct task_struct *target, kernel_cap_t *effective, 194 kernel_cap_t *inheritable, kernel_cap_t *permitted) 195 { 196 const struct cred *cred; 197 198 /* Derived from kernel/capability.c:sys_capget. */ 199 rcu_read_lock(); 200 cred = __task_cred(target); 201 *effective = cred->cap_effective; 202 *inheritable = cred->cap_inheritable; 203 *permitted = cred->cap_permitted; 204 rcu_read_unlock(); 205 return 0; 206 } 207 208 /* 209 * Determine whether the inheritable capabilities are limited to the old 210 * permitted set. Returns 1 if they are limited, 0 if they are not. 211 */ 212 static inline int cap_inh_is_capped(void) 213 { 214 215 /* they are so limited unless the current task has the CAP_SETPCAP 216 * capability 217 */ 218 if (cap_capable(current_cred(), current_cred()->user->user_ns, 219 CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) 220 return 0; 221 return 1; 222 } 223 224 /** 225 * cap_capset - Validate and apply proposed changes to current's capabilities 226 * @new: The proposed new credentials; alterations should be made here 227 * @old: The current task's current credentials 228 * @effective: A pointer to the proposed new effective capabilities set 229 * @inheritable: A pointer to the proposed new inheritable capabilities set 230 * @permitted: A pointer to the proposed new permitted capabilities set 231 * 232 * This function validates and applies a proposed mass change to the current 233 * process's capability sets. The changes are made to the proposed new 234 * credentials, and assuming no error, will be committed by the caller of LSM. 235 */ 236 int cap_capset(struct cred *new, 237 const struct cred *old, 238 const kernel_cap_t *effective, 239 const kernel_cap_t *inheritable, 240 const kernel_cap_t *permitted) 241 { 242 if (cap_inh_is_capped() && 243 !cap_issubset(*inheritable, 244 cap_combine(old->cap_inheritable, 245 old->cap_permitted))) 246 /* incapable of using this inheritable set */ 247 return -EPERM; 248 249 if (!cap_issubset(*inheritable, 250 cap_combine(old->cap_inheritable, 251 old->cap_bset))) 252 /* no new pI capabilities outside bounding set */ 253 return -EPERM; 254 255 /* verify restrictions on target's new Permitted set */ 256 if (!cap_issubset(*permitted, old->cap_permitted)) 257 return -EPERM; 258 259 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ 260 if (!cap_issubset(*effective, *permitted)) 261 return -EPERM; 262 263 new->cap_effective = *effective; 264 new->cap_inheritable = *inheritable; 265 new->cap_permitted = *permitted; 266 return 0; 267 } 268 269 /* 270 * Clear proposed capability sets for execve(). 271 */ 272 static inline void bprm_clear_caps(struct linux_binprm *bprm) 273 { 274 cap_clear(bprm->cred->cap_permitted); 275 bprm->cap_effective = false; 276 } 277 278 /** 279 * cap_inode_need_killpriv - Determine if inode change affects privileges 280 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV 281 * 282 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV 283 * affects the security markings on that inode, and if it is, should 284 * inode_killpriv() be invoked or the change rejected? 285 * 286 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and 287 * -ve to deny the change. 288 */ 289 int cap_inode_need_killpriv(struct dentry *dentry) 290 { 291 struct inode *inode = dentry->d_inode; 292 int error; 293 294 if (!inode->i_op->getxattr) 295 return 0; 296 297 error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); 298 if (error <= 0) 299 return 0; 300 return 1; 301 } 302 303 /** 304 * cap_inode_killpriv - Erase the security markings on an inode 305 * @dentry: The inode/dentry to alter 306 * 307 * Erase the privilege-enhancing security markings on an inode. 308 * 309 * Returns 0 if successful, -ve on error. 310 */ 311 int cap_inode_killpriv(struct dentry *dentry) 312 { 313 struct inode *inode = dentry->d_inode; 314 315 if (!inode->i_op->removexattr) 316 return 0; 317 318 return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); 319 } 320 321 /* 322 * Calculate the new process capability sets from the capability sets attached 323 * to a file. 324 */ 325 static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, 326 struct linux_binprm *bprm, 327 bool *effective, 328 bool *has_cap) 329 { 330 struct cred *new = bprm->cred; 331 unsigned i; 332 int ret = 0; 333 334 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) 335 *effective = true; 336 337 if (caps->magic_etc & VFS_CAP_REVISION_MASK) 338 *has_cap = true; 339 340 CAP_FOR_EACH_U32(i) { 341 __u32 permitted = caps->permitted.cap[i]; 342 __u32 inheritable = caps->inheritable.cap[i]; 343 344 /* 345 * pP' = (X & fP) | (pI & fI) 346 */ 347 new->cap_permitted.cap[i] = 348 (new->cap_bset.cap[i] & permitted) | 349 (new->cap_inheritable.cap[i] & inheritable); 350 351 if (permitted & ~new->cap_permitted.cap[i]) 352 /* insufficient to execute correctly */ 353 ret = -EPERM; 354 } 355 356 /* 357 * For legacy apps, with no internal support for recognizing they 358 * do not have enough capabilities, we return an error if they are 359 * missing some "forced" (aka file-permitted) capabilities. 360 */ 361 return *effective ? ret : 0; 362 } 363 364 /* 365 * Extract the on-exec-apply capability sets for an executable file. 366 */ 367 int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) 368 { 369 struct inode *inode = dentry->d_inode; 370 __u32 magic_etc; 371 unsigned tocopy, i; 372 int size; 373 struct vfs_cap_data caps; 374 375 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); 376 377 if (!inode || !inode->i_op->getxattr) 378 return -ENODATA; 379 380 size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, 381 XATTR_CAPS_SZ); 382 if (size == -ENODATA || size == -EOPNOTSUPP) 383 /* no data, that's ok */ 384 return -ENODATA; 385 if (size < 0) 386 return size; 387 388 if (size < sizeof(magic_etc)) 389 return -EINVAL; 390 391 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); 392 393 switch (magic_etc & VFS_CAP_REVISION_MASK) { 394 case VFS_CAP_REVISION_1: 395 if (size != XATTR_CAPS_SZ_1) 396 return -EINVAL; 397 tocopy = VFS_CAP_U32_1; 398 break; 399 case VFS_CAP_REVISION_2: 400 if (size != XATTR_CAPS_SZ_2) 401 return -EINVAL; 402 tocopy = VFS_CAP_U32_2; 403 break; 404 default: 405 return -EINVAL; 406 } 407 408 CAP_FOR_EACH_U32(i) { 409 if (i >= tocopy) 410 break; 411 cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); 412 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); 413 } 414 415 return 0; 416 } 417 418 /* 419 * Attempt to get the on-exec apply capability sets for an executable file from 420 * its xattrs and, if present, apply them to the proposed credentials being 421 * constructed by execve(). 422 */ 423 static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) 424 { 425 struct dentry *dentry; 426 int rc = 0; 427 struct cpu_vfs_cap_data vcaps; 428 429 bprm_clear_caps(bprm); 430 431 if (!file_caps_enabled) 432 return 0; 433 434 if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) 435 return 0; 436 437 dentry = dget(bprm->file->f_dentry); 438 439 rc = get_vfs_caps_from_disk(dentry, &vcaps); 440 if (rc < 0) { 441 if (rc == -EINVAL) 442 printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", 443 __func__, rc, bprm->filename); 444 else if (rc == -ENODATA) 445 rc = 0; 446 goto out; 447 } 448 449 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); 450 if (rc == -EINVAL) 451 printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", 452 __func__, rc, bprm->filename); 453 454 out: 455 dput(dentry); 456 if (rc) 457 bprm_clear_caps(bprm); 458 459 return rc; 460 } 461 462 /** 463 * cap_bprm_set_creds - Set up the proposed credentials for execve(). 464 * @bprm: The execution parameters, including the proposed creds 465 * 466 * Set up the proposed credentials for a new execution context being 467 * constructed by execve(). The proposed creds in @bprm->cred is altered, 468 * which won't take effect immediately. Returns 0 if successful, -ve on error. 469 */ 470 int cap_bprm_set_creds(struct linux_binprm *bprm) 471 { 472 const struct cred *old = current_cred(); 473 struct cred *new = bprm->cred; 474 bool effective, has_cap = false; 475 int ret; 476 477 effective = false; 478 ret = get_file_caps(bprm, &effective, &has_cap); 479 if (ret < 0) 480 return ret; 481 482 if (!issecure(SECURE_NOROOT)) { 483 /* 484 * If the legacy file capability is set, then don't set privs 485 * for a setuid root binary run by a non-root user. Do set it 486 * for a root user just to cause least surprise to an admin. 487 */ 488 if (has_cap && new->uid != 0 && new->euid == 0) { 489 warn_setuid_and_fcaps_mixed(bprm->filename); 490 goto skip; 491 } 492 /* 493 * To support inheritance of root-permissions and suid-root 494 * executables under compatibility mode, we override the 495 * capability sets for the file. 496 * 497 * If only the real uid is 0, we do not set the effective bit. 498 */ 499 if (new->euid == 0 || new->uid == 0) { 500 /* pP' = (cap_bset & ~0) | (pI & ~0) */ 501 new->cap_permitted = cap_combine(old->cap_bset, 502 old->cap_inheritable); 503 } 504 if (new->euid == 0) 505 effective = true; 506 } 507 skip: 508 509 /* if we have fs caps, clear dangerous personality flags */ 510 if (!cap_issubset(new->cap_permitted, old->cap_permitted)) 511 bprm->per_clear |= PER_CLEAR_ON_SETID; 512 513 514 /* Don't let someone trace a set[ug]id/setpcap binary with the revised 515 * credentials unless they have the appropriate permit 516 */ 517 if ((new->euid != old->uid || 518 new->egid != old->gid || 519 !cap_issubset(new->cap_permitted, old->cap_permitted)) && 520 bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { 521 /* downgrade; they get no more than they had, and maybe less */ 522 if (!capable(CAP_SETUID)) { 523 new->euid = new->uid; 524 new->egid = new->gid; 525 } 526 new->cap_permitted = cap_intersect(new->cap_permitted, 527 old->cap_permitted); 528 } 529 530 new->suid = new->fsuid = new->euid; 531 new->sgid = new->fsgid = new->egid; 532 533 if (effective) 534 new->cap_effective = new->cap_permitted; 535 else 536 cap_clear(new->cap_effective); 537 bprm->cap_effective = effective; 538 539 /* 540 * Audit candidate if current->cap_effective is set 541 * 542 * We do not bother to audit if 3 things are true: 543 * 1) cap_effective has all caps 544 * 2) we are root 545 * 3) root is supposed to have all caps (SECURE_NOROOT) 546 * Since this is just a normal root execing a process. 547 * 548 * Number 1 above might fail if you don't have a full bset, but I think 549 * that is interesting information to audit. 550 */ 551 if (!cap_isclear(new->cap_effective)) { 552 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || 553 new->euid != 0 || new->uid != 0 || 554 issecure(SECURE_NOROOT)) { 555 ret = audit_log_bprm_fcaps(bprm, new, old); 556 if (ret < 0) 557 return ret; 558 } 559 } 560 561 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 562 return 0; 563 } 564 565 /** 566 * cap_bprm_secureexec - Determine whether a secure execution is required 567 * @bprm: The execution parameters 568 * 569 * Determine whether a secure execution is required, return 1 if it is, and 0 570 * if it is not. 571 * 572 * The credentials have been committed by this point, and so are no longer 573 * available through @bprm->cred. 574 */ 575 int cap_bprm_secureexec(struct linux_binprm *bprm) 576 { 577 const struct cred *cred = current_cred(); 578 579 if (cred->uid != 0) { 580 if (bprm->cap_effective) 581 return 1; 582 if (!cap_isclear(cred->cap_permitted)) 583 return 1; 584 } 585 586 return (cred->euid != cred->uid || 587 cred->egid != cred->gid); 588 } 589 590 /** 591 * cap_inode_setxattr - Determine whether an xattr may be altered 592 * @dentry: The inode/dentry being altered 593 * @name: The name of the xattr to be changed 594 * @value: The value that the xattr will be changed to 595 * @size: The size of value 596 * @flags: The replacement flag 597 * 598 * Determine whether an xattr may be altered or set on an inode, returning 0 if 599 * permission is granted, -ve if denied. 600 * 601 * This is used to make sure security xattrs don't get updated or set by those 602 * who aren't privileged to do so. 603 */ 604 int cap_inode_setxattr(struct dentry *dentry, const char *name, 605 const void *value, size_t size, int flags) 606 { 607 if (!strcmp(name, XATTR_NAME_CAPS)) { 608 if (!capable(CAP_SETFCAP)) 609 return -EPERM; 610 return 0; 611 } 612 613 if (!strncmp(name, XATTR_SECURITY_PREFIX, 614 sizeof(XATTR_SECURITY_PREFIX) - 1) && 615 !capable(CAP_SYS_ADMIN)) 616 return -EPERM; 617 return 0; 618 } 619 620 /** 621 * cap_inode_removexattr - Determine whether an xattr may be removed 622 * @dentry: The inode/dentry being altered 623 * @name: The name of the xattr to be changed 624 * 625 * Determine whether an xattr may be removed from an inode, returning 0 if 626 * permission is granted, -ve if denied. 627 * 628 * This is used to make sure security xattrs don't get removed by those who 629 * aren't privileged to remove them. 630 */ 631 int cap_inode_removexattr(struct dentry *dentry, const char *name) 632 { 633 if (!strcmp(name, XATTR_NAME_CAPS)) { 634 if (!capable(CAP_SETFCAP)) 635 return -EPERM; 636 return 0; 637 } 638 639 if (!strncmp(name, XATTR_SECURITY_PREFIX, 640 sizeof(XATTR_SECURITY_PREFIX) - 1) && 641 !capable(CAP_SYS_ADMIN)) 642 return -EPERM; 643 return 0; 644 } 645 646 /* 647 * cap_emulate_setxuid() fixes the effective / permitted capabilities of 648 * a process after a call to setuid, setreuid, or setresuid. 649 * 650 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of 651 * {r,e,s}uid != 0, the permitted and effective capabilities are 652 * cleared. 653 * 654 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective 655 * capabilities of the process are cleared. 656 * 657 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective 658 * capabilities are set to the permitted capabilities. 659 * 660 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 661 * never happen. 662 * 663 * -astor 664 * 665 * cevans - New behaviour, Oct '99 666 * A process may, via prctl(), elect to keep its capabilities when it 667 * calls setuid() and switches away from uid==0. Both permitted and 668 * effective sets will be retained. 669 * Without this change, it was impossible for a daemon to drop only some 670 * of its privilege. The call to setuid(!=0) would drop all privileges! 671 * Keeping uid 0 is not an option because uid 0 owns too many vital 672 * files.. 673 * Thanks to Olaf Kirch and Peter Benie for spotting this. 674 */ 675 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) 676 { 677 if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && 678 (new->uid != 0 && new->euid != 0 && new->suid != 0) && 679 !issecure(SECURE_KEEP_CAPS)) { 680 cap_clear(new->cap_permitted); 681 cap_clear(new->cap_effective); 682 } 683 if (old->euid == 0 && new->euid != 0) 684 cap_clear(new->cap_effective); 685 if (old->euid != 0 && new->euid == 0) 686 new->cap_effective = new->cap_permitted; 687 } 688 689 /** 690 * cap_task_fix_setuid - Fix up the results of setuid() call 691 * @new: The proposed credentials 692 * @old: The current task's current credentials 693 * @flags: Indications of what has changed 694 * 695 * Fix up the results of setuid() call before the credential changes are 696 * actually applied, returning 0 to grant the changes, -ve to deny them. 697 */ 698 int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) 699 { 700 switch (flags) { 701 case LSM_SETID_RE: 702 case LSM_SETID_ID: 703 case LSM_SETID_RES: 704 /* juggle the capabilities to follow [RES]UID changes unless 705 * otherwise suppressed */ 706 if (!issecure(SECURE_NO_SETUID_FIXUP)) 707 cap_emulate_setxuid(new, old); 708 break; 709 710 case LSM_SETID_FS: 711 /* juggle the capabilties to follow FSUID changes, unless 712 * otherwise suppressed 713 * 714 * FIXME - is fsuser used for all CAP_FS_MASK capabilities? 715 * if not, we might be a bit too harsh here. 716 */ 717 if (!issecure(SECURE_NO_SETUID_FIXUP)) { 718 if (old->fsuid == 0 && new->fsuid != 0) 719 new->cap_effective = 720 cap_drop_fs_set(new->cap_effective); 721 722 if (old->fsuid != 0 && new->fsuid == 0) 723 new->cap_effective = 724 cap_raise_fs_set(new->cap_effective, 725 new->cap_permitted); 726 } 727 break; 728 729 default: 730 return -EINVAL; 731 } 732 733 return 0; 734 } 735 736 /* 737 * Rationale: code calling task_setscheduler, task_setioprio, and 738 * task_setnice, assumes that 739 * . if capable(cap_sys_nice), then those actions should be allowed 740 * . if not capable(cap_sys_nice), but acting on your own processes, 741 * then those actions should be allowed 742 * This is insufficient now since you can call code without suid, but 743 * yet with increased caps. 744 * So we check for increased caps on the target process. 745 */ 746 static int cap_safe_nice(struct task_struct *p) 747 { 748 int is_subset; 749 750 rcu_read_lock(); 751 is_subset = cap_issubset(__task_cred(p)->cap_permitted, 752 current_cred()->cap_permitted); 753 rcu_read_unlock(); 754 755 if (!is_subset && !capable(CAP_SYS_NICE)) 756 return -EPERM; 757 return 0; 758 } 759 760 /** 761 * cap_task_setscheduler - Detemine if scheduler policy change is permitted 762 * @p: The task to affect 763 * 764 * Detemine if the requested scheduler policy change is permitted for the 765 * specified task, returning 0 if permission is granted, -ve if denied. 766 */ 767 int cap_task_setscheduler(struct task_struct *p) 768 { 769 return cap_safe_nice(p); 770 } 771 772 /** 773 * cap_task_ioprio - Detemine if I/O priority change is permitted 774 * @p: The task to affect 775 * @ioprio: The I/O priority to set 776 * 777 * Detemine if the requested I/O priority change is permitted for the specified 778 * task, returning 0 if permission is granted, -ve if denied. 779 */ 780 int cap_task_setioprio(struct task_struct *p, int ioprio) 781 { 782 return cap_safe_nice(p); 783 } 784 785 /** 786 * cap_task_ioprio - Detemine if task priority change is permitted 787 * @p: The task to affect 788 * @nice: The nice value to set 789 * 790 * Detemine if the requested task priority change is permitted for the 791 * specified task, returning 0 if permission is granted, -ve if denied. 792 */ 793 int cap_task_setnice(struct task_struct *p, int nice) 794 { 795 return cap_safe_nice(p); 796 } 797 798 /* 799 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from 800 * the current task's bounding set. Returns 0 on success, -ve on error. 801 */ 802 static long cap_prctl_drop(struct cred *new, unsigned long cap) 803 { 804 if (!capable(CAP_SETPCAP)) 805 return -EPERM; 806 if (!cap_valid(cap)) 807 return -EINVAL; 808 809 cap_lower(new->cap_bset, cap); 810 return 0; 811 } 812 813 /** 814 * cap_task_prctl - Implement process control functions for this security module 815 * @option: The process control function requested 816 * @arg2, @arg3, @arg4, @arg5: The argument data for this function 817 * 818 * Allow process control functions (sys_prctl()) to alter capabilities; may 819 * also deny access to other functions not otherwise implemented here. 820 * 821 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented 822 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM 823 * modules will consider performing the function. 824 */ 825 int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, 826 unsigned long arg4, unsigned long arg5) 827 { 828 struct cred *new; 829 long error = 0; 830 831 new = prepare_creds(); 832 if (!new) 833 return -ENOMEM; 834 835 switch (option) { 836 case PR_CAPBSET_READ: 837 error = -EINVAL; 838 if (!cap_valid(arg2)) 839 goto error; 840 error = !!cap_raised(new->cap_bset, arg2); 841 goto no_change; 842 843 case PR_CAPBSET_DROP: 844 error = cap_prctl_drop(new, arg2); 845 if (error < 0) 846 goto error; 847 goto changed; 848 849 /* 850 * The next four prctl's remain to assist with transitioning a 851 * system from legacy UID=0 based privilege (when filesystem 852 * capabilities are not in use) to a system using filesystem 853 * capabilities only - as the POSIX.1e draft intended. 854 * 855 * Note: 856 * 857 * PR_SET_SECUREBITS = 858 * issecure_mask(SECURE_KEEP_CAPS_LOCKED) 859 * | issecure_mask(SECURE_NOROOT) 860 * | issecure_mask(SECURE_NOROOT_LOCKED) 861 * | issecure_mask(SECURE_NO_SETUID_FIXUP) 862 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) 863 * 864 * will ensure that the current process and all of its 865 * children will be locked into a pure 866 * capability-based-privilege environment. 867 */ 868 case PR_SET_SECUREBITS: 869 error = -EPERM; 870 if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) 871 & (new->securebits ^ arg2)) /*[1]*/ 872 || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ 873 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ 874 || (cap_capable(current_cred(), 875 current_cred()->user->user_ns, CAP_SETPCAP, 876 SECURITY_CAP_AUDIT) != 0) /*[4]*/ 877 /* 878 * [1] no changing of bits that are locked 879 * [2] no unlocking of locks 880 * [3] no setting of unsupported bits 881 * [4] doing anything requires privilege (go read about 882 * the "sendmail capabilities bug") 883 */ 884 ) 885 /* cannot change a locked bit */ 886 goto error; 887 new->securebits = arg2; 888 goto changed; 889 890 case PR_GET_SECUREBITS: 891 error = new->securebits; 892 goto no_change; 893 894 case PR_GET_KEEPCAPS: 895 if (issecure(SECURE_KEEP_CAPS)) 896 error = 1; 897 goto no_change; 898 899 case PR_SET_KEEPCAPS: 900 error = -EINVAL; 901 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ 902 goto error; 903 error = -EPERM; 904 if (issecure(SECURE_KEEP_CAPS_LOCKED)) 905 goto error; 906 if (arg2) 907 new->securebits |= issecure_mask(SECURE_KEEP_CAPS); 908 else 909 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); 910 goto changed; 911 912 default: 913 /* No functionality available - continue with default */ 914 error = -ENOSYS; 915 goto error; 916 } 917 918 /* Functionality provided */ 919 changed: 920 return commit_creds(new); 921 922 no_change: 923 error: 924 abort_creds(new); 925 return error; 926 } 927 928 /** 929 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted 930 * @mm: The VM space in which the new mapping is to be made 931 * @pages: The size of the mapping 932 * 933 * Determine whether the allocation of a new virtual mapping by the current 934 * task is permitted, returning 0 if permission is granted, -ve if not. 935 */ 936 int cap_vm_enough_memory(struct mm_struct *mm, long pages) 937 { 938 int cap_sys_admin = 0; 939 940 if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, 941 SECURITY_CAP_NOAUDIT) == 0) 942 cap_sys_admin = 1; 943 return __vm_enough_memory(mm, pages, cap_sys_admin); 944 } 945 946 /* 947 * cap_file_mmap - check if able to map given addr 948 * @file: unused 949 * @reqprot: unused 950 * @prot: unused 951 * @flags: unused 952 * @addr: address attempting to be mapped 953 * @addr_only: unused 954 * 955 * If the process is attempting to map memory below dac_mmap_min_addr they need 956 * CAP_SYS_RAWIO. The other parameters to this function are unused by the 957 * capability security module. Returns 0 if this mapping should be allowed 958 * -EPERM if not. 959 */ 960 int cap_file_mmap(struct file *file, unsigned long reqprot, 961 unsigned long prot, unsigned long flags, 962 unsigned long addr, unsigned long addr_only) 963 { 964 int ret = 0; 965 966 if (addr < dac_mmap_min_addr) { 967 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, 968 SECURITY_CAP_AUDIT); 969 /* set PF_SUPERPRIV if it turns out we allow the low mmap */ 970 if (ret == 0) 971 current->flags |= PF_SUPERPRIV; 972 } 973 return ret; 974 } 975